What I wished I'd said...
Years and years ago I was flying from the Raleigh-Durham area to the Freeway Airport in a Cessna 172, and went through the Andrews Airforce Base airspace. It was late at night, and nobody else was on the frequency when I requested permission to go through their airspace.
Permission was granted.
There was a pretty strong headwind (more than I had expected), and the controller casually mentioned that my ground speed was 80 knots.
If I had been a little more bold, I would have told him that my indicated airspeed was 120 knots, and that if I wanted to go any faster I'd probably have to get out and push.
Wish I'd said it, as he sounded a little bored.
Plus I had to sprint for the telephone to close my flight plan in time once I landed, so giving him a heads up would have helped if the headwind had delayed me by a few minutes more.